Everywhere he goes lately, Barack Obama begins his stump speech with a story about a four-year-old boy named Sammy. The tale comes from Sammy’s parents, who brought him along when they met Obama’s campaign manager, Jim Messina. There was a picture of Obama on the wall, and the parents asked their son if he recognized the leader of the free world. He did. “What does Barack Obama do?” they asked Sammy, according to Obama’s retelling. And Sammy replies: “He approves this message.”

It’s a funny little ice-breaker, a knowing wink at the negative ads filling flat screens in swing states. But it’s also a bridge to the message itself, which is that Obama wants to emphasize the middle class as the foundation of a strong economy, whereas Romney’s top-down economics benefits the rich. The message is the same every time, almost down to the word.

By contrast, Mitt Romney‘s message has lately seemed to change on a weekly basis. For months, Romney’s campaign marketed the election as a referendum on Obama, and sold their candidate as a businessman with the savvy to orchestrate an economic recovery. It wasn’t enough. (And even then, the referendum wasn’t solely that.) So this summer, around the time that Romney selected Paul Ryan as his running mate, they recast the campaign as a choice between two different political visions: one that emphasizes government, and one that is skeptical of it. That hasn’t gone so well either.

Now, at a do-or-die juncture for Romney, the campaign still can’t decide which frame it prefers. It seems stuck in a messaging purgatory, with elements of column A (referendum) muddled by those from column B (choice). Romney’s latest ad buys often clash with the message he’s driving in interviews and public events. Rather than home in on a single winning formula, he has grasped for new ones almost daily, veering from Libya to China to debt to coal in a frantic scramble for a theme that sticks.

In a conference call with reporters Monday morning, the Romney campaign unveiled what may be its closing argument: We can’t afford another four years like the last four years. “This is a theme that we’re going to integrate across every aspect our campaign,” said senior adviser Kevin Madden. The campaign will drive it, he said, at the upcoming debates, rallies in battleground states and in paid media.

This sounds like a referendum. But wait. On each of the salient issues — taxes, spending, jobs, energy, regulations, health care, national security — Romney will “lay out the importance choices” voters face by contrasting Obama’s plan with his own, Madden said. Part of that focus, he added, will be “what the country will look like under a President Romney and how we’ll be better off.”

If this sounds confusing, you’re not alone. The first question on the conference call came from a veteran of the Romney beat, who asked the campaign to reconcile the difference between its simple message and the panoply of topics that preceded it. “They all fit under one umbrella,” explained senior adviser Ed Gillespie, who then proceeded to rattle off all the policy areas on which Obama has failed and to which “we cannot afford four more years like the last four” applies.

To be sure, Obama’s message has also changed radically over the course of the campaign. Not long ago, the Obama team’s indictment of Romney was that he was driven by nothing so much as political expedience; in the parlance of Democratic consultants, he lacked a “core.” Late last spring, that characterization was replaced by a new version of Romney, the heartless villain with purportedly extreme views. As caricatures go, this was almost a 180. But once the Obama team made the change, they stuck to it. If the past few months are any indication, Romney will have a new bumper sticker by the end of the week.